1. Field of the Invention
This invention relates to an improved process for the production of linear crystalline polymers of aralkyl halides and to the polymer compositions produced thereby. In particular, this invention relates to a process for preparing crystalline polybenzyls and alkyl substituted derivatives thereof, which crystalline polybenzyls have melting points not heretofore obtainable. More particularly, this invention relates to the low temperature, polymerization of .alpha.-alkylbenzyl halides in the presence of a complex of a Friedel-Crafts catalyst and a complexing agent which is nitroalkane or a nitroarene. The polymerizable .alpha.-alkylbenzyl halides which can be readily employed are represented by the following structural formula: ##STR1## wherein R.sub.1 is a C.sub.1 -C.sub.4 alkyl group, R.sub.2 and R.sub.3 are the same or different and are each selected from the group consisting of hydrogen and C.sub.1 -C.sub.4 alkyl groups and X is halogen. Still more particularly, this invention relates to the polymerization of benzyl halides in the presence of a complex of a Friedel-Crafts catalyst and a complexing agent which can be a nitroalkane or a nitroarene at temperatures of between about -65.degree. C. to about -40.degree. C.
2. Description of the Prior Art
The polymerization of benzyl halides in the presence of Friedel-Crafts catalyst is well known in the art. See, for example, Ralph A. Jacobson, "Polymers from Benzyl Chloride and Related Compounds", J. Amer. Chem. Soc., 54, 1513 (1932); O. C. Dermer et al, "Catalysts for the Polymerization of Benzyl Chloride", J. Amer. Chem. Soc., 63, 3525 (1941); H. C. Haas et al, "Polybenzyl Type Polymers", J. Pol. Sci., 15, 503 (1955); C. Friedel et al, "Comments in a Meeting", Bull. Soc. Chim. France, 43, 53 (1885); and N. N. Lebedev et al, "High Molecular Weight Compound XXII the Polycondensation of Benzyl Chloride", J. Gen. Chem., USSR, English translation, 19, 647 (1949). Depending on the Friedel-Crafts catalyst employed for the polymerization of the polybenzyls, the resins obtained were more or less insoluble in benzene or soluble in benzene, have softening points over the range of about 75.degree. C. to 80.degree. C. and melt at about 95.degree. C. and were branched.
It is also known to use catalysts such as metal powders, oxides or aluminum alkyls for the polymerization of benzyl chloride. See, for example, E. J. Spanier et al, "Condensation of Benzyl Chloride Catalized by Group II Metals", J. Pol. Sci., A-1, 7, 2679 (1969); M. Iovu et al, "Catalytic Reactions with Alkyl-Metal Halides V. Polycondensation of Benzyl Chloride", Analele Univ. C. I. Parhon, Ser. Stiint, Nat., 9, 189 (1960); M. Iovu, "Polycondensation Reactions with Organo-Aluminum Catalysts", Rev. Chim. (Bucharest), 14, 385 (1963); and A. Yamada et al, "Poly(Benzyl Chloride I. Polymerization of Benzyl Chloride by Use of Triethylaluminum as Catalyst", Riku. Gaku Kenkyusho Hikiku, 37, 445 (1961). The polymers prepared in the presence of metal powders, oxides or aluminum alkyls are generally highly branched, low molecular weight amorphous resins.
U.S. Pat. No. 3,346,514 of Isaacson et al, issued Oct. 10, 1967, discloses a method of preparing polybenzyls in the presence of a Group IVB to VIB and Group VIII transition metal compound and a Group I to III organometal reducing agent. The yields obtainable under the disclosed method is relatively low, the molecular weights obtainable are quite low and although the disclosure discusses the crystallinity of the polybenzyls the crystallinity obtainable is nevertheless low.
In U.S. Pat. No. 3,418,259 of Kennedy et al there is disclosed a process of producing polybenzyls in the presence of a Friedel-Crafts catalyst. The process involves using very low temperatures, i.e., about -130.degree.. The process obtains polybenzyls in extremely low yields and having very low molecular weights and low levels of crystallinity. Furthermore, because of the low molecular weights obtained, i.e., less than about 6700, the polymers formed very brittle films.